The present invention relates generally to low voltage, high current electrical power distribution systems, and more particularly to a fused electrical disconnect device for use in an electrical power distribution system.
Power distribution systems, such as telephone switching offices in telecommunications systems are often constructed on a large scale to serve many customers. Since telephone communications are essential for most businesses, it is necessary to ensure that telecommunications systems of this nature are highly reliable. To keep telecommunications systems operational in the event of power interruptions, most telecommunications systems typically include a plurality of high-capacity storage batteries to provide electrical power for operating telecommunications equipment whenever power from the conventional power sources becomes unavailable.
In these telecommunications systems, batteries and power converters are usually connected together so that operating telecommunications equipment are supplied with power from a collection of sources. Notwithstanding this, it is desirable to be capable of isolating individual pieces of telecommunications equipment (or small groups thereof) from the power sources in order to perform maintenance and installation activities. It is also desirable to provide overload protection for telecommunications equipment on an individual basis.
Common overload protection devices for telecommunications equipment fall into two categories namely, fused electrical disconnect devices and circuit breakers. Fused electrical disconnect devices are typically connected to a power distribution panel interconnecting the power source supply buss and the load telecommunications equipment and include replaceable fuses that interrupt power when an overload or fault condition exists. When an overload or fault condition occurs and the fuse in the fused electrical disconnect device blows, the fuse must be removed from the fused electrical disconnect device and replaced before current flow to the telecommunications equipment can be resumed. Many variations of fused electrical disconnect devices exist. For example, a fused electrical disconnect device that includes an alarm fuse and a protection fuse is disclosed in U.S. Pat. No. 5,355,274 to Marach et al.
Circuit breakers typically include plug-in type connectors and are plugged into power distribution panels interconnecting load telecommunications equipment and the power source supply buss. Similar to fused electrical disconnect devices, circuit breakers also interrupt power when an overload or fault condition exists but can be manually reset to resume current flow to the telecommunications equipment without requiring the circuit breakers to be removed from the power distribution panels.
The connection interfaces and relative sizes of fused electrical disconnect devices and circuit breakers have, to-date, been radically different. As a result, it has not been possible to install circuit breakers in power distribution systems originally set up for use with fused electrical disconnect devices. The converse has also been true. Thus, switching the type of overload protection devices used in power distribution systems in the past has been costly and time consuming, making it impractical.
It is therefore an object of the present invention to provide a novel fused electrical disconnect device.
According to one aspect of the present invention there is provided a fused electrical disconnect device comprising:
a housing;
a line plug-in connector and a load plug-in connector, said line and load connectors extending from one side of said housing and being adapted to mate with complementary connectors in a power distribution panel; and
a load protection fuse element removably insertable into said housing to establish an electrical current path between said line connector and said load connector.
In the preferred embodiment, the load protection fuse is carried by a fuse holding cartridge removably insertable into the housing. The fused electrical disconnect device further includes an alarm terminal extending from the housing. The alarm terminal is provided with an alarm signal when the electrical current path is interrupted. Preferably, the fuse holding cartridge also carries an alarm fuse. The alarm fuse provides the alarm signal to the alarm terminal when the load protection fuse fails to complete the electrical current path.
It is also preferred that the alarm signal is provided to the alarm terminal when the fuse holding cartridge is removed from the housing. Preferably, the housing accommodates a contact switch that electrically couples the line connector and the alarm terminal when the fuse holding cartridge is removed from the housing.
Preferably, the housing includes retaining notches therein to engage with retainers on the power distribution panel to inhibit the fused electrical disconnect device from being treated as a simple pull out connector. It is also preferred that the plug-in connectors are releasably secured to the housing to enable the fused electrical disconnect device to be wired to the power distribution panel in a conventional manner.
According to another aspect of the present invention there is provided a fused electrical disconnect device comprising:
a compact housing;
a line plug-in connector and a load plug-in connector, said line and load connectors extending from one side of said housing and being adapted to mate with complementary connectors in a power distribution panel;
an alarm terminal extending from said housing and being positioned between said line and load connectors;
a line conductive path within said housing and being electrically connected to said line connector;
a load conductive path within said housing and being electrically connected to said load connector;
a load protection fuse removeably insertable into said housing to complete an electrical current path between said line and load conductive paths; and
an alarm fuse connected in parallel to said load protection fuse, said alarm fuse providing an alarm signal to said alarm terminal when said electrical current path is interrupted.
According to yet another aspect of the present invention there is provided a fused electrical disconnect device comprising:
a housing;
a line plug-in connector and a load plug-in connector, said line and load connectors extending from one side of said housing;
a line buss within said housing and being electrically connected to said line connector;
a load buss within said housing and being electrically connected to said load connector;
a fuse holding cartridge removably insertable into said housing, said fuse holding cartridge including:
a body;
line and load terminal blades extending from one side of said body, said line terminal blade contacting said line buss and said load terminal blade contacting said load buss when said fuse holding cartridge is inserted into said housing; and
a load protection fuse removably insertable between said line and load terminal blades to establish an electrical current path between said line and load terminal blades; and
a circuit within said housing to detect when said fuse holding cartridge is removed from said housing.
The present invention provides advantages in that the connection interface of the fused electrical disconnect device includes plug-in type connectors similar to those commonly used in circuit breakers. The plug-in type connectors allow the fused electrical disconnect device to be front mounted in a power distribution panel adapted to accommodate plug-in type connectors quickly and easily. This of course avoids having to wire the fused electrical disconnect device between the load device and the power source supply buss.
The present invention also provides advantages in that the fused electrical disconnect device generates an alarm signal whenever power to the load device is interrupted. Power interruption can be a result of a blown fuse within the fused electrical disconnect device or a removal of the fuse holding cartridge from the housing. Since the fused electrical disconnect provides an alarm signal when the fuse holding cartridge is removed from the device housing, situations where the fuse holding cartridge has been removed from the housing but not replaced can be detected.